Utility providers are using digital meters in order to gather qualitative and quantitative data regarding the services provided to consumers. Use of these meters is increasing in an effort to correlate charges and costs of the service provided to consumers.
These meters are in more and more use now-a-days owing to the fact that digital meters provide more accurate measurement and billing over the conventional meters. Further, digital meters allow service providers to track additional parameters, such as peak usage. These digital meters also facilitate constant monitoring and providing utility as per demand. Thus, use of digital meters has resulted in a cost effective solution on part of consumers and has also proved convenient to service providers allowing them to plan their resources better.
Earlier it was required to read the digital meters by direct visual observation by going on to the point of installation. To save manpower and time, the electric meter industry has developed wireless communication circuitry which can transmit and receive data signals over wireless networks. Signals are transmitted and received through an antenna. The antenna may be installed as an external or an internal component of the wireless utility meter.
An external antenna may be subjected to tampering. Further, functioning of external antenna may be affected by weather conditions also. Hence, an internal antenna (“under the glass”) is favored for use with utility meters and technologies are known for manufacturing meters with built-in antennas. These antennas are typically placed inside the product enclosure and sealed for environmental and certification reasons.
It is known that the digital and power conversion circuits inside a utility meter radiate wideband noise that overlaps the receive band of the cellular modem or other radio receivers used for wireless data communications. This results in degraded total isotropic sensitivity (TIS) in the radio receiver that causes some meters to fall short of sensitivity standards required by CTIA, cellular carriers and other regulatory bodies. This problem exists for all “under the glass” utility meters because the antenna has to be within the outer cover of the utility meter and hence, always very close to the noise source.
Present products attempt to improve the TIS of antennas for wireless utility meters by adjusting the position of the antenna away from sources of noise or by installing radio frequency (RF) shielding cans or other noise reduction methods (such as spread spectrum oscillators or RF bypass capacitors).
U.S. Pat. No. 7,459,986 describes a method of reducing noise generated by the circuitry.
Another problem is the emission of secondary radiation at harmonic frequencies of the primary radiation. This secondary radiation is emitted by semiconductor devices present inside the utility meter when excited by primary radiation from the antenna. Because of the non-linear volt-ampere characteristics of semiconductor devices, this secondary radiation contains harmonics of the fundamental frequency being emitted by the antenna. This secondary radiation at harmonic frequencies causes utility meters to fail Radiated Spurious Emissions (RSE) standards mandated by PTCRB and other regulatory bodies.
U.S. Pat. No. 7,372,373 describes a method of reducing harmonic frequency radiation from a printed circuit board or a telemetry module.
Present products attempt to reduce RSE by using RF shields and RF bypass capacitors but the metrology and register boards inside utility meters are usually already in production so installing shields or RF bypass capacitors on them is not an option.
However, prior techniques of noise and radiation reduction suffer from a number of shortcomings. In, particular, the conventional systems and methods do not provide an effective method of noise and radiation reduction without contributing to the existing problem.